Electromagnetic control device



Nov. 25, 1952 F. KESSELRING ELECTROMAGNETIC CONTROL DEVICE Filed Aug. 1, 1946 INVENTOR.

AT-TO A EYJ Fritz Kes selr|ng BY Patented Nov. 25, 1952 UNITED STATES PATENT OFFICE Application August 1, 1946, Serial No. 687,625 In Switzerland August 7, 1945 2 Claims.

This invention relates to electromagnetic contactors for controlling electric load circuits, and in a more particular aspect to devices that separate their switch contacts in relation to the instantaneous value of the current to be controlled.

It is an object of my invention to provide circuit controlling switching devices capable of high duty performance in power circuits that operate at a higher switching speed and secure a more reliable arc de-ionization than heretofore obtainable. Another, related, object is to more safely prevent during the contact separating performance the occurrence of back arcing due to voltage recurring across the contact gap. Still another object of the invention is to reduce the movable masses of an electromagnetic contactor to a minimum, thus also minimizing the inertia and increasing the acceleration and speed of the magnetically controlled operation far beyond the corresponding magnitudes of known electromagnetic contactors. An object of the invention is also to devise a high-duty electromagnetic contactor capable of completing its circuit opening movement within a switching interval in the order of seconds.

According to the invention, devices of the above-mentioned kind are equipped with a plurality of contactor armatures that are electrically and magnetically arranged in parallel relation to one another. In this manner the current to be interrupted at each individual armature is kept within moderate limits. However, in such parallel armature arrangements, the several parallel arcs initially occurring at the contact opening moment may become reduced, due to asymmetrical load distribution, to only two series arcs at the two contact surfaces of a single armature which is then subjected to severe thermal stress. In order to prevent this, a plurality of loadcurrent leads extend separately and insulated from each other through laminated iron stack to the respective stationary contacts of the circuit breaker so that an asymmetric current distribution will cause a magnetic induction which, during the current interrupting performance, tends to sustain the individual parallel connected arcs. An induction magnitude as small as 10* henrys or less was found suflicient to attain the desired effect, and a length of the mutually insulated parallel leads Within the laminated iron pack of not more than approximately 10 centimeters is usually satisfactory.

The foregoing and more specific objects and features of my invention will be apparent from the following description in conjunction with the drawing showing an axial sectional view of a highduty current interrupter according to the invention.

The illustrated device has two pairs of stationary contacts 2|, 22, to cooperate with two armatures 22, disposed at the ends of respective leads 23, 24. These leads are all insulated from one another and pass through narrow holes of laminated magnetic pole structures 25, 25 so as to be coupled with one another by magnetic induction. Insulating plates 21 are attached to the magnetic poles 25 and 26. An insulating wall 28 forms part of a housing for the movable circuit breaker parts. This housing is completely sealed by means of iron sheets 29 and 30 which are soldered to the end surfaces of the insulating wall 28. The housing is closely surrounded by another insulating wall 3! of cylindrical shape. Inside the cylinder 3! is a magnetic yoke 32 to which the leads 33 and 24 are secured. A part 34 of the magnetic circuit is connected to the outgoing line 35. An operating field coil 36 is connected to the secondary winding 31 of a transformer 38 whose primary winding 39 is fed by a battery Ail through a control switch 4|. As mentioned, the transformer 38 serves to isolate the high-voltage contactor from the control circuit of switch 4| and also permits limiting and timing the period of contactor field excitation, as will be understood from the operation described below. A closing coil 42 for switch 4! is connected to the power circuit by means (not shown) for synchronous control. The armatures 22 are mounted on torsionally elastic pivot pins. The spring bias normally holds the armatures in the illustrated contact-closed position.

The operation of the device is as follows: Assume that about 1O sec. before the current wave passes through zero the synchronous control means energize the coil 42 which closes switch 4| in a few l0* sec. As the current in the primary winding 39 is building up, a voltage is induced in the secondary 31 and excites the coil 36, thus producing a magnetic field which traverses the armatures 22 and closes itself through the insulating cylinder 3 l. Due to this field, the armatures 22 start turning counterclockwise toward the insulating plates 21. The arcs now occurring between the stationary contacts 20, 2| and the armatures are stabilized by the inductive reaction in the connecting leads 23, 24 and are extinguished, at the latest, when the current wave passes through zero. The cooling and cleionization is concentrated on the contact surfaces, that is, in the direction of the axis of the arcs. At the instant when the current passes through zero, the armatures are still moving and have reached a high velocity, whereby the increase in dielectric strength or breakdown voltage between the separating contact surfaces is kept higher than required to prevent the recurrence of an arc. At the end of the opening movement, the armatures abut against the insulating plates 21. In the open position of the armatures a disconnecting switch (not shown) is opened. Shortly thereafter the current in primary 39 has reached its full value so that the voltage of secondary 31 drops to zero and the coil 36 becomes deenergized, thus permitting the armatures 22 to return to the illustrated positions.

It will be noted that the armatures and stationary contacts are disposed within a housing whose side walls consist of insulating material and whose axial ends are closed by the pole pieces of the magnetic circuit. This housing, preferably, is'hermetically sealed. The iron sheet covers 29 and 89 serve to secure such a seal. If, for instance, the Wall 28 is made of porcelain or glass,

7 its end faces may be covered with a thin metal coating to which the iron sheets 29, 30 are soldered. Such a hermetically sealed housing can be filled with gas, preferably hydrogen, of a pressure of 4 to 10 kg/cm Under these conditions and at small breaking distances of one-tenth of a millimeter, increased values of breakdown voltage are obtained ranging from 10,000 to 20,- 000 volts. In other cases it may be preferred to provide a high vacuum in the housing.

A tubular insulator as shown at 3! is desirable for high-voltage operation because it increases the insulation and creep distance between the two power leads 33, 35. This insulator 3| should have high dielectric strength, for instance, 30 kilovolts per millimeter.

It should be understood that the example described above is presented by way of illustration and not by way of limitation and may be varied and modified without departing from the essential features of my invention and within the scope of the claims annexed hereto.

I claim:

1. An electromagnetic control device, comprising two mutually insulated terminals for connection into a circuit to be controlled, an electromagnet having two pole faces facing each other, a plurality of revolvable armatures disposed between said two pole faces in magnetic parallel relation to each other and individually biased to an angular position away from said pole faces and simultaneously movable by said electromagnet toward said pole faces into another angular position, pairs of stationary contact means engageable by said respective armatures when said armatures are in one of said positions so that then each armature electrically bridges the appertaining pair of stationary contact means, each pair having two leads connected with said respective terminals so that said leads and armatures are electrically parallel connected between said terminals, the leads connected to the same one of said terminals being insulated from each other, said electromagnet having a stack of magnetizable laminations, and said leads extending through said stack.

2. An electromagnetic control device, comprising two mutually insulated terminals for connection into a circuit to be controlled, an electromagnet having two pole faces facing each other, a plurality of armatures disposed between said two pole faces in magnetic parallel relation to each other and individually biased to a position away from said pole faces and simultaneously movable by said electromagnet toward said pole faces into another position, pairs of stationary contact means engageable by said respective armatures when said armatures are in one of said positions so that then each armature electrically bridges the appertaining pair of stationary contact means, each pair having two leads connected with said respective terminals so that said leads and armatures are electrically parallel connected between said terminals, the leads connected to the same one of said terminals being insulated from each other, said electromagnet having a stack of magnetizable laminations, and said leads extending through said stack.

FRITZ KESSELRING.

REFERENCES CETED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 490,178 Thomson Jan. 17, 1893 684,378 Potter Oct. 8, 1901 969,345 Culver Sept. 6, 1910 1,315,886 Wall Sept. 9, 1919 1,426,993 Kardaetz Aug. 22, 1922 1,694,223 Lemmon Dec. 4, 1928 1,706,782 Hilliard Mar. 26, 1929 1,769,674 Brandt July 1, 1930 1,814,851 Prince July 14, 1931 1,819,207 Slepian Aug. 18, 1931 1,820,808 Kearsley Aug. 25, 1931 1,843,615 Lyle Feb. 2, 1932 2,279,536 Thommen Apr. 14, 1942 2,391,672 Boehne et al Dec. 25, 1945 2,445,401 Langer July 20, 1948 2,453,555 Thommen Nov. 9, 1948 2,499,632 Coake Mar. 7, 1950 FOREIGN PATENTS Number Country Date 451,596 Germany Oct. 28, 1927 

